Chemical-mechanical polishing (CMP) is the term used to refer to a process that is used in semiconductor manufacture. As its name implies, the CMP process is typically used in semiconductor processing to polish (e.g., planarize) the surface of the semiconductor wafer. The CMP process is relatively new in that, until recently, conventional processes were sufficient with the comparatively low circuit densities involved. However, increases in circuit densities (e.g., the transition from wafers having 0.25 micron features to 0.18 micron features, and even to 0.045 micron features) have forced the need to develop new processes for planarizing the wafer, of which CMP has become favored. Similarly, the more recent shift away from aluminum interconnect technology to copper interconnect technology has further favored the use of CMP to polish (e.g., planarize) semiconductor wafers.
Briefly, the chemical-mechanical polishing (CMP) process involves scrubbing a semiconductor wafer with a pad in the presence of a chemically reactive slurry that contains abrasive particles. As its name implies, the polishing action of the chemical-mechanical polishing (CMP) process is both chemical and mechanical. Chemicals aid in material removal by modifying the surface film while abrasion between the surface particles, pad, and the modified film facilitates mechanical removal. It is believed that this synergistic interplay between the chemical and mechanical components in the process is the key to effective polishing of the CMP process.
While the CMP process is being increasingly used in semiconductor manufacturing processes, the CMP process remains poorly understood, and the exact mechanisms though which the process works have not been determined. For example, while certain parameters for the CMP process have been developed that are satisfactory for wafers utilizing aluminum interconnect technology, those same process parameters have not proven to be particularly satisfactory for use with wafers utilizing copper interconnect technology. One important requirement of a successful CMP slurry for copper is a high polish rate. High polish rates lead to shorter copper overburden polishing times.